<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        #foo  ul:first-of-type > li:nth-of-type(even) {
            color: red;
        }
        </style>
</head>
<body>
    <div id="foo">
        <p>Countries</p>
        <ul>
            <li>China</li>
            <li>Japan</li>
            <li>Korea</li>
        </ul>
        <p>Age</p>
        <ul>
            <li>13</li>
            <li>17</li>
            <li>20</li>
        </ul>
    </div>
    <script>
                var b = "hello world"
                console.log(b.indexOf(a))
                var a = 123;
            console.log(a.toString(2))
    </script>
</body>
</html>